Electric discharge device and method of manufacture



Jan. 2, 1940. CHARLTON 2,185,832

ELECTRIC DISCHARGE DEVICE AND METHOD OF MANUFACTURE Original Filed Aug. 10, 1925 Inventor: Ewnest E .Chariton,

Patented Jan. 2, 1940 UNITED STATES ELECTRIC DISCHARGE DEVICE AND METH- OD OF MANUFACTURE Ernest E. Charlton, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Division of application Serial No. 49,164, August 10, 1925. This application November 1, 1934,

Serial No. 751,048

Claims.

The present invention relates to the manufactureof electrical discharge devices and more particularly to an improved method of conditioning such devices by the introduction, through flashing, of a highly reactive material or getter adapted to combine with objectionable gases previously driven ofi from the electrodes and associated conducting parts.

This application is a division of an application Serial No. 49,164, filed August 10, 1925, by Dow O. 'Whelan and me jointly, entitled Electric discharge devices and methods of manufacture" and issued as Patent 2,054,030, granted September 8, 1936. I 15. In accordance with a convenient method described in my Patent No. 1,738,420, granted De cember 3, 1929, a metal of this character has been introduced by evolution from a mixture capable of evolving the desired metal when chemical reaction is caused therein, the mixture being applied with a suitable binder upon one of the electrodes of the device. The electrode may be heated to a reaction temperature by electron bombardment, by high frequency induction or 25 otherwise.

In accordance with Patent No. 2,054,030, above referred to, certain improvements have been provided in the practice of this method by placing the charge to be vblatilized in a nearly closed capsule which is adapted to be heated to a desired temperature. According to my present invention a further improvement is obtained by locating the getter capsule in close proximity to the electrode structure but in such a position in the envelope that it may be heated by electric induction independently of the electrodes in the device. For example, the capsule may be arranged at such angle to the main electrodes that a high frequency coil may be placed independent-' ly in inductive relation to the capsule or to the electrodes.

The main advantages of this improvement are as follows:

(1) A paste or binder to secure the material to be vaporized on a support is not required, thus avoiding the introduction of foreign material from which deleterious gas may emanate.

(2) The solid by-products of a chemical re action in the charge are held within the capsule where they can do no harm.

(3) The electrodes, particularly the plate, can be degasified before the reactive vapor is produced in the device.

(4) The charge evolving the desired metal may be heated after the electrodes have been denuded of gas and may be heated by high frequency induction without reheating the electrodes to a substantial degree.

The present invention is illustrated by the 'one of the alkali metals, into a vacuum tube of the radio detector or amplifier type, such as shown in Fig. 1. This tube includes in a sealed container I ,the usual electrodes comprising a filamentary cathode 2 connected to leading-in wires 3, 4 and anchored upon a support 5, also a grid 6 mounted upon the supports I, 8 and con nected to a sealed-in conductor 9 and an anode or plate I0, which is mounted upon the wires II, I2, and connected to a leading-in conductor I3. The base terminals for these various electrode members have been merely indicated at I4.

-As more clearly shown in Fig. 2, a capsule I5 is mounted upon the anode I0 by spot welding or other convenient means. As shown in Fig. 6, this capsule consists of two disk-shaped parts I6, I'I connected by av narrow neck portion I8. The disk I6 is slightly concave and is provided with two small cars I9, 20. These parts may be stamped by a single operation out of thin sheet metal, and should consist ,of material such as nickel and molybdenum which may be heated to the reaction temperature of a charge placed therein without danger of being itself volatilized. The charge of material or getter, from which the volatilizable ingredient is obtained, is laced in the concave or dished portion of the disk I6 and the disk I! is closed upon it as a cover, as shown in Fig. 7, the ears I9, beingbent over to holdthetwo parts of the capsule in fixed relation. This capsule then is introduced into the tube either by mounting directly upon one of the electrodes, as shown in Fig. 2, or by mounting the capsule upon a suitable stem 2 I, as shown in Figs. 3 and 4. In some cases the capsule may be made tubular in shape, such as shown in Fig. 8. In this case afianged portion 22 is provided at the rim of the tube upon which a cover 23 may be applied by welding or otherwise. The flanged portion 22 may be attached directly to the anode, as indicated in Fig. 5, or may be otherwise mounted, for example, as has been illustrated in Figs. 3 and 4 with respect to the diskshaped capsule. The tubular portion of the capsule shown in Fig. 8 preferably is provided with nearly closed slits through which vapor may escape.

In Fig. 9 is shown a tubular capsule 24 which is carriedby one'of the lateral supports 25 of an anode 26, and which contains two pellets 21 of reaction mixture. The ends of the capsule are crimped to hold the charge 21 in place while leaving crevices for the escape of vapor. The stem 28, the grid 29, and other parts of the tube, are merely indicated for the sake of clearness.

When a reactive charge, such as a mixture of a chloride of caesium or other alkali metal, and a reducing agent such as metallic calcium or magnesium, is to be placed in the capsule, the ingredients preferably are first compacted. into coherent form. For example, the mixture may be formed as a strip by extrusion under heavy hydraulic pressure, the strip later being subdivided in convenient lengths. The material is carefully dried as by baking in a vacuum and is maintained in a dry condition until ready for use. Just before the assembly of the difierent parts of the vacuum tube, a pellet of this dry mixture is placed in the capsule, which then is closed, as described, and mounted in the vacuum tube.

In the form shown in Figs. 3, 4 and 9, the capsules l5 may be heated by high frequency independently of the anode l0 because of their location in such a position that the high inducing frequency coil (not shown) may be placed about the vacuum tube so as first to produce preferential inductive heating of the anode to degasify the anode without appreciably heating the capsule. The high frequency coil then may be placed in'such a position with respect to the capsule that the latter is heated to a temperature at which a reaction occurs in the charge within the capsule, resulting in the volatilization of the alkali metal or whatever material is generated by the reaction, the vapor penetrating through the crevices in the capsule into the evacuated space of the container 8. For example, in the case of the construction shown in Fig. 3 in which the capsule I5 is spaced away from the plate 90, the inducing high frequency coil first is placed about the plate to bake it out. After the gases evolved by this bake-out have been evacuated, the orientation of the inducing coil is changed by placing it at right angles to the capsule and sumcient current is induced therein to heat the charge to a reaction temperature. In the case of the construction shown in Fig. 4, the coil also is first placed about the plate and then may be either lowered or is placed about the capsule from the side of the tube that is in a direction normal to the plate. The tube may be sealed off at an appropriate time in accordance with known practlce.

It is advantageous in some cases to volatilize a material which is capable of combining with gas, such as calcium or magnesium, during the bake-out of the anode or plate. I have indicated at 39 in Figs. 4 and 5, a piece of ribbon of magnesium or the like, fastened to the plate where it will be volatilized when the plate is heated to drive out gases.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The method of preparing electrical discharge devices having metal parts inclosed within an envelope which consists in inductively heating said metal parts to remove the gases therefrom and later vaporizing a getter previously aflixed to one of said metal parts in such a position as to be substantially without the: field of inductive effect employed in previously heating the said metal parts whereby said metal parts may be first inductively heated and said getter may be later inductively vaporized by the eflect of a subsequently applied inductive field displaced from efiect inductive heating of the said conductive parts without causing flashing of the getter, and thereafter producing a magnetic field of such location and strength as to cause suflicient inductive heating of the getter to result in flashing thereof.

3. The method of conditioning an electrical discharge device having electrically conductive parts enclosed within an envelope, which method includes placing a getter within the envelope in close proximity to the said conductive parts but so positioned with respect thereto as to facilitate preferential inductive heating of the said parts without simultaneous flashing of the getter, applying to said device a magnetic field of such orientation as to cause such preferential heating of the said conductive parts, and thereafter changing the orientation of the applied magnetic field to produce sufiicient inductive heating of the getter to result in flashing the same.

4. The method of conditioning an electrical discharge device having electrode structure enclosed within an envelope, which method comprises positioning a getter in effective heat-exchanging relation with an electrically conductive member of such character as to be readily heated by inductive means, placing the said member and getter within the envelope in close proximity to the electrode structure but in such relation thereto as to facilitate inductive heating of the structure without the simultaneous occurrence of sufficient heating of the said conductive member to result in flashing of the getter, applying to the device a magnetic field of such location and strength as to cause inductive heating of the electrode structure without simultaneous flashing of the getter, and therafter applying to the device a magnetic field of such location and strength as to result in strong inductive heating of the said conductive member. and resultant flashing of the said getter.

5. The method of conditioning an electrical discharge device having electrically conductive parts enclosed within an envelope, which method comprises positioning a getter within a metallic member of such form as at least partially to enclose the getter, placing the said member within the envelope in close proximity to the said conductive parts but sufiiciently thermally isolated therefrom to facilitate preferential inductive heating of the parts without simultaneous flashing of the getter, producing a magnetic field of such location and strength as to cause such preferential heating of the said conductive parts, and thereafter producing a magnetic field of such location and strength as to causesufllcient inductive heating of the said metallic member to eflect flashing of the getter.

ERNEST E. CHARLTON. 

